Multi-electrode gas-filled discharge tubes



United States l atent O 3,025,427 MULTI-ELECTRODE GAS-FILLED DEQHARGE TUBES Alan Turner and William Arthur Revitt, Beeston, Nottingham, England, assignors to Ericsson Telephones Limited, London, England, a British company Filed May 23, 1960, Ser. No. 30,996 14 (Claims. Cl. Mia-1&8)

The present invention relates to multi-electrode gasfilled discharge tubes of the type having a central electrode around which is arranged a plurality of surrounding electrodes, in operation glow discharges being struck between the central electrode and selected ones of the surrounding electrodes. Usually the central electrode is an anodeand the surrounding electrodes are cathodes for the reason that the glow of the discharge is a cathode glow and accordingly that one of the surrounding electrodes at which a discharge is taking place can be seen. However, the central electrode may be a cathode and the surrounding electrodes anodes.

Tubes of the type specified are described in the specifications of our British Patents Nos. 712,171, 712,215 and 777,362 and sold under our registered trademark Deltatron, for example.

According to the present invention the central electrode of a tube of the type specified is supported on a metal rod which extends down the tube and passes through the base of the tube, the portion of the rod protruding through the base of the tube constituting the valve pin by means of which potential is, in operation, applied to the central electrode, the surrounding electrodes being aligned with respect to the central electrode by means of an insulating structure mounted on the rod.

The electrodes and insulating structure preferably form a coaxial structure, the rod lying along the axis of the structure, though it may be offset from the axis. More than one rod can be used to support the central electrode, at least one rod extending through the base of the tube to form a valve pin.

This construction enables a rigid electrode structure to be made without the use of the customary glass pinch. The base of the tube can consist solely of a disc of glass through which the said rod and the pins to which the surrounding electrodes are connected pass. This leads to a tube of less height than those having a conventional base including a glass pinch The insulating structure preferably contacts the envelope of the tube at a number of points, further to steady the electrode structure.

The surrounding electrodes can be wires arranged arranged around a cylindrical surface and substantially parallel to the central rod. The pins for these electrodes can be disposed in substantially the same cylindrical surface and the wires constituting the surrounding electrodes can then extend downwardly to their pins and be welded thereto.

In many tubes of the type specified numbers of the surrounding electrodes are connected together. Such connection may be effected by terminating all but one of the electrodes to be connected in a group at a metal disc sandwiched in the insulating structure, the remaining one electrode extending down to a valve pin as well as being connected to the metal disc.

The invention will now be described by way of example with reference to the accompanying drawings in which:

FIG. 1 is a side view of a gas-filled selector tube, and

FIG. 2 is a cross-section on the line HH of FIG. 1.

A gas-filled selector tube comprises a disc of glass 1% through which the valve or terminal pins for the tube are spasm Patented Mar. 13, 1962 sealed. One terminal pin is in the form of a long straight rod 11 passing centrally through the disc and extending axially upwards through the tube to the upper region of the envelope T2. The envelope is in the form of a domed glass cylinder sealed at its open edges to the glass disc. The other terminal pins 13 are seventeen in number and are arranged in a ring around the central pin 11 at 20 intervals. There is accordingly a gap of 40 between two of the pins and this gap enables the tube to be correctly located in a valve holder. A disc-like anode 14 is welded to the top of the central electrode.

The anode i4 is surrounded by forty cathodes 15 which consist of wires arranged in a cylindrical surface coaxial with the rod 11 with their upper ends substantially in the plane of the anode 14. Of the forty cathodes every fourth one is an independent cathode 15a and extends right down to one of the circle of pins 13 and is welded thereto. The thirty remaining cathodes are connected in three groups of ten and constitute first, second and third guide electrodes. The arrangement is such that the cathodes follow a repeating order of independent cathode, first guide electrode, second guide electrode, third guide electrode, independent cathode The cathodes are aligned in fixed relationship with respect to and uniformly spaced from the anode by means of an insulating structure mounted on the rod 11 forming the central pin. A ceramic sleeve 16 surrounds the lower part of the rod and rests against the base of the tube. Stacked on top of the sleeve are four centrally apertured ceramic discs 17, 18, 19 and 20 and a further ceramic sleeve 21 surrounds that part of the rod extending between the uppermost disc and the anode. The uppermost disc 20 is of a diameter only a little less than the inside diameter of the envelope. The other three ceramic discs are of reduced diameter. The forty cathodes 15 pass through a ring of perforations 22 in the uppermost ceramic disc 2%). A disc 23 of mica is sandwiched between the discs 18 and 19, and has perforations corresponding to those in the uppermost ceramic disc and is also provided with a plurality of small triangular cars 24 which engage the glass envelope and help to maintain the electrode structure steady.

A thin sheet metal disc 25 is sandwiched between the third and the uppermost ceramic discs 19 and 20. This metal disc has ten small ears 26 lying beneath the perforations in the uppermost disc through which the first guide electrodes pass and bent down over the edge of the disc 19. Nine of the first guide electrodes terminate at these cars and are welded thereto. The tenth of the first guide electrodes is welded to its corresponding ear, but extends downwardly through a perforation in the mica disc to one of the circle of valve pins 13. The ten second guide electrodes pass through perforations in the mica disc and are similarly welded to a second cared metal disc 27 sandwiched between the mica disc 23 and the ceramic disc 18. One of the second guide electrodes 15b extends right down to one of the valve pins 13. The third guide electrodes are Welded to a third cared metal disc 28 sandwiched between the discs 17 and 18, one electrode extending down to a pin. The three sheet metal discs have central apertures of such size that there is no risk of a discharge taking place between the rod supporting the anode any any one of the discs.

Getter supports 29 are welded to two of the remaining valve pins. It will be seen that there are two of the seventeen surrounding valve pins which are not used.

The materials of the electrodes may be as customarily employed in the manufacture of multi-electrode gas-filled discharge tubes and the envelope is filled with a gas of a composition and under a pressure as is usually employed in such tubes.

It will be obvious that a structure substantially the same as that shown in the drawings could be used where there are only two sets of guide electrodes or where all of the cathodes previously called independent cathodes but one are connected together (as for example in tubes for use as counters). As another example of a tube to which the structure of the present invention can be applied reference may be had to the specification of British Patent No. 721,058. This describes a tube in which some of the guide electrodes are provided with separate valve pins and are not connected internally to the other guide electrodes. Such a tube may be so connected in circuit that carry signals for stepping the discharge in succeeding and preceding stages in a cascade counter are derived from the separate guide electrodes, rather than from one (or more) of the cathodes, with certain consequent advantages.

We claim:

1. A multi-electrode discharge tube comprising a sealed envelope including a base portion, a filling of gas in the envelope and an electrode structure within the envelope, the said structure comprising a central electrode and a ring of electrodes round the central electrode, terminal means for making electrical connections to said ring of electrodes, a continuous metal rod sealed through the base portion of the envelope to provide a portion thereof projecting from the envelope to constitute a terminal pin for the central electrode, the central electrode being fixed to the end of the metal rod Within the envelope in electrically conductive relationship, and an insulating structure mounted on the metal rod between the central electrode and the base portion of the envelope and supporting the ring of electrodes in spaced relationship with the central electrode.

2. A discharge tube according to claim 1, wherein the insulating structure comprises a plurality of protuberances which contact the envelope further to steady the said electrode structure.

3. A multi-electrode discharge tube comprising a sealed tubular envelope including a base portion, a filling of gas in the envelope and a coaxial electrode structure within the envelope, the said structure comprising a central electrode and a ring of electrodes round the central electrode, terminal means for making electrical connections to said ring of electrodes, a continuous metal rod on the axis of the coaxial electrode structure and of the tubular envelope and sealed through the base portion of the envelope to provide a portion thereof projecting from the envelope to constitute a terminal pin for the central electrode, the central electrode being fixed to the end of the metal rod within the envelope in electrically conductive relationship, and an insulating structure mounted on the metal rod between the central electrode and the base portion of the envelope and supporting the ring of electrodes in spaced relationship with the central electrode.

4. A multi-electrode discharge tube comprising a sealed envelope including a glass disc base portion, a filling of gas in the envelope andan electrode structure within the envelope, the said structure comprising a central electrode and a ring of electrodes round the central electrode, terminal means for making electrical connections to said ring of electrodes, 2. continuous metal rod sealed through the glass disc base portion of the envelope to provide a portion thereof projecting from the envelope to constitute a terminal pin for the central electrode, the central electrode being fixed to the end of the metal rod within the envelope in electrically conductive relationship, and an insulating structure mounted on the metal rod between the central electrode and the base portion of the envelope and supporting the ring of electrodes in spaced relationship with the central electrode.

5. A multi-electrode discharge tube comprising a sealed envelope including a base portion, a filling of gas in the envelope and an electrode structure within the envelope, the said structure comprising a central electrode and a ring of parallel electrode rods defining a cylindrical pattern round the central electrode, terminal means for making electrical connections to said ring of electrodes, a continuous metal rod parallel to the electrode rods sealed through the base portion of the envelope to provide a portion thereof projecting from the envelope to constitute a terminal pin for the central electrode, the central electrode being fixed to the end of the metal rod within the envelope in electrically conductive relationship, and an insulating structure mounted on the metal rod between the central electrode and the base portion of the envelope and supporting the ring of electrodes in spaced relationship with the central electrode.

6. A discharge tube according to claim 5, wherein said terminal means comprises a plurality of terminal pins lying substantially in the said cylindrical pattern and sealed through the base portion of the envelope, at least some of the electrode rods extending continuously down to respective terminal pins and being attached thereto.

7. A multi-electrode discharge tube comprising a sealed envelope including a base portion, a filling of gas in the envelope and an electrode structure within the envelope, the said structure comprising a central electrode and a ring of electrodes round the central electrode, terminal means for making electrical connections to said ring of electrodes, a continuous metal rod sealed through the base portion of the envelope to provide a portion thereof projectng from the envelope to constitute a terminal pin for the central electrode, the central electrode being mechanically fixed to the end of the metal rod within the envelope in electrically conductive relationship, and an insulating structure mounted on the metal rod between the central electrode and the base portion of the envelope and comprising a stack of ceramic plates through which the metal rod passes centrally, at least one of the plates having a ring of apertures through which the electrodes in the said ring thereof pass, respectively, whereby the positions of the electrodes relative to the central electrode are defined.

8. A discharge tube according to claim 7, comprising a metal disc sandwiched between two of the ceramic plates, certain of the electrodes in said ring being connected to the metal disc, said terminal means including a terminal pin sealed through said envelope base portion and including means for electrically connecting the last'mentioned pin to the metal disc.

9. A discharge tube according to claim 8, wherein one of said certain electrodes extends continuously between and electrically interconnects the metal plate and the lastmentioned terminal pin.

10. A discharge tube according to claim 9, wherein said ring electrodes extend generally parallel to one another and said metal disc includes a plurality of gears at the periphery thereof welded to said certain electrodes, respectively.

11. A multi-electrode discharge tube comprising a sealed envelope, an electrode structure within said envelope comprising a main electrode and a plurality of electrodes positioned to define respective discharge spaces with respect to said main electrode, terminal means for making electrical connections to said plurality of electrodes, a continuous metal rod within the envelope supportingly fixed in electrically conductive relationship to said main electrode and sealed through said envelope with a portion of said rod projecting from the envelope to constitute a terminal pin for the main electrode, and an insulatng structure mounted on said metal rod and supporting said plurality of electrodes in fixed relationship with respect to the main electrode.

12. A discharge tube according to claim 11, wherein said insulating structure comprises a stack of insulating plates through which said metal rod passes centrally, at least one of the plates having a plurality of apertures through which the plurality of electrodes extend, respectively, a sheet metal member sandwiched between two of the insulating plates, certain of said plurality of electrodes being connected to said sheet metal member, said terminal means including a terminal pin sealed through said envelope and including means for electrically connecting the last-mentioned pin to said sheet metal member within the envelope.

13. A discharge tube according to claim 12, wherein one of said certain electrodes extends continuously past said sheet metal member and is electrically connected directly to the last-mentioned terminal pin.

14. A multi-electrode gas-filled discharge tube comprising a tube envelope, a central electrode including a metal disc and a metal rod supporting and electrically connected to said disc and extending generally perpendicular thereto, a plurality of electrodes surrounding said central electrode providing respective discharge spaces therebetween, terminal means for making electrical connections to said plurality of electrodes, said metal rod extending continuously from said disc through said envelope in sealed relationship therewith and projecting therefrom to constitute a terminal pin for the central electrode, and an insulating structure mounted on said metal rod Within said envelope to support the plurality of electrodes in fixed relationship with the central electrode.

Acton Sept. 1, 1953 Williams July 21, 1959 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,025,427 March 13, 1962 Alan Turner et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

In the heading to the printed specification, between 11nes 7 and 8,1nsert Claims priority, application Great Britain June 9, 1959 Signed and sealed this 30th day of October 1962.

(SEAL) Attest:

ERNEST w. SWIDER DAVID LADD Attesting Officer Commissioner of Patents 

